1. Field of the Invention
The present invention relates, generally, to lighting controls, and, more particularly, to providing a single ballast that is operable to efficiently support a plurality of different fluorescent lamp types.
2. Description of the Related Art
Typically, gas discharge lamps, such as fluorescent lamps, must be driven by ballasts in order to illuminate. An important parameter of an electronic ballast is the ballast factor. The ballast factor is particularly important in the design of a fluorescent lighting system. A typical fluorescent lamp is rated by the manufacturer to provide a rated light output (e.g., measured in lumens) at a rated lamp current. The ballast factor is used to determine the actual maximum possible light output for a particular lamp-ballast combination. As used herein, the ballast factor refers to the ratio of the actual maximum light output of a particular lamp (driven by a particular ballast) to the rated maximum light output of the particular lamp, i.e.,
      Ballast    ⁢                  ⁢    Factor    =            Actual      ⁢                          ⁢      maximum      ⁢                          ⁢      lamp      ⁢                          ⁢      output      ⁢                          ⁢              (                  in          ⁢                                          ⁢          lumens                )                    Rated      ⁢                          ⁢      maximum      ⁢                          ⁢      lamp      ⁢                          ⁢      output      ⁢                          ⁢              (                  in          ⁢                                          ⁢          lumens                )            For example, a ballast factor of 1.0 indicates that the maximum amount of light actually provided by a lamp-ballast combination is equal to the possible maximum amount of light output rated by the lamp manufacturer. In the prior art, the ballast factor of a particular ballast is a permanent, unchangeable and fixed value, and is used and relied upon during lighting design calculations.
Moreover, energy efficient lighting design is useful for the design and corresponding energy consumption in buildings and other structures. For example, designers need to know the constraints of devices associated with lighting systems in order to provide appropriate light at all times.
Unfortunately, a ballast having a ballast factor rated for a particular lamp type may not be interchangeable with another lamp type with a different rating. While a single ballast may operate to strike and regulate lamp arc current for two different lamp types, the efficiency of the ballast—particularly with respect to power consumption and relative light output of the two lamps—vastly differs, effectively precluding the possibility of using a single model ballast for a plurality of different lamp types.
In typical prior art lighting control systems, three wires are often used to transmit analog signals (such as phase-control signals) to a master control unit to control lamps and other electrical load devices. Typically, the phase-control signals are transmitted over three wires and enable the dimming of lamps and the controlling of other electrical devices.
More recently, electronic ballasts have been provided with microprocessors, which enable the transmission and reception of digital commands for control of fluorescent lamps. An example of such an electronic ballast is described in commonly-assigned U.S. patent application Ser. No. 10/824,248, filed Apr. 14, 2004, entitled, MULTIPLE-INPUT ELECTRONIC BALLAST WITH PROCESSOR, and U.S. patent application Ser. No. 11/011,933, filed Dec. 14, 2004, entitled DISTRIBUTED INTELLIGENCE BALLAST SYSTEM AND EXTENDED LIGHTING CONTROL PROTOCOL. The entire disclosures of both applications are incorporated herein by reference. The microprocessors may be programmed to turn the ballasts on and off in response to outputs provided by various sensors, such as occupancy sensors and light sensors. The ballasts may be programmed via wireless infrared (“IR”) or radio frequency (“RF”) signals, which may include commands to program ballasts to operate individually or in groups, and in response to signals received from photosensors, occupancy sensors or other sources.
The electronic ballasts of a fluorescent lighting control system may transmit and receive commands via a digital ballast communication link using the industry-standard digital addressable lighting interface (“DALI”) protocol. Such fluorescent lighting control systems provide significant energy savings by operating in connection with occupancy sensors, supporting daylight harvesting, and implementing load-shedding techniques. Users of such systems by receive tax credits from the government, and other incentives from electric utility companies in connection, for example, with reductions in power consumption per square foot, per light fixture, or per location, or in reductions in total power consumption. Moreover, a business may garner positive good will and good public relations in response to taking active measures to reduce power consumption and implement so-called “green” policies.
As known in the art, a ballast drives a fluorescent lamp by initially establishing a lamp arc current and, thereafter, regulating the arc current to ensure proper operation of the lamp. Each fluorescent lamp is provided with a rated maximum possible light output that is determined by the lamp manufacturer. A respective ballast factor set by the ballast manufacturer directly affects the actual light output for a particular fluorescent lamp. For example, depending upon a respective ballast factor, a forty-watt lamp may produce more light output (e.g., measured in lumens) than a sixty-watt lamp that is driven by a ballast with a lower ballast factor.
Techniques are known for limiting the maximum light output of a fluorescent lamp by adjusting the “high-end trim” of the electronic dimming ballast driving the lamp. The high-end trim defines the maximum light intensity to which the fluorescent lamp may be controlled. The high-end trim is preferably determined by an end user of the ballast. For example, a building manager may program the high-end trim via commands transmitted over the digital ballast communication link. The high-end trim limits the dimming range of the electronic dimming ballast by establishing the maximum value. The dimming range of the electronic dimming ballast is typically rescaled between the high-end trim and a low-end trim (i.e., the minimum intensity to which the fluorescent lamp may be controlled, which is typically off). For example, if the high-end trim of a ballast is set to 75%, the maximum amount of light output available from the fluorescent lamp is effectively limited to 75% of the rated output of the lamp/ballast combination, and the dimming range of the ballast is rescaled between 0% and 75%.
Unlike defining a high-end trim, a ballast factor is typically a non-adjustable, permanently set value that is provided by a ballast manufacturer. In one context, the ballast factor is used by lighting designers, for example, in calculations made during building lighting design. From an input standpoint, the ballast factor represents (and affects) power consumption. The input factor, as known in the art, represents an amount of power consumption by a load and is proportional to the ballast factor. Lighting designers rely upon the ballast factor of each respective ballast to calculate the amount of light output that a fixture will produce. Further, the ballast factor is used by designers, for example, to determine an appropriate number of lighting fixtures and the corresponding light output therefor. Accurate knowledge of these and other variables enables the designer to make significant cost savings decisions, such as to eliminate one or more lighting fixtures.
In addition to lighting designers, other parties have a particular interest in power consumption variables that are considered during the design and manufacture of a building or other structure. For example, parties with a particular interest in power consumption, such as specialists informed of building and electrical codes (e.g., the National Electric Code or NEC), also use ballast factors to calculate expected energy use and consumption.
Because high-end trim values can be changed by end users, for example, using hand-held programming devices or making selections on a master control unit, building lighting designers do not take the high-end trim value set by an end user into account during the lighting design process. Similarly, electrical code review personnel do not consider high-end trim values when determining or assessing an estimated amount of power that a building is expected to use. High-end trim values are relatively easy to change, and parties who are provided with relatively low levels of authorization may be able to set or modify the high-end trim value associated with a lighting fixture. In view of the possibility that a high-end trim value can be modified, particularly by parties having relatively low security authorization levels, lighting designers and electrical code review personnel do not rely upon high-end trim values for building lighting design and accurate estimates of expected energy consumption.
Recently, lighting fixtures have been designed with improved reflective properties that increase efficiency and ensure corresponding reductions in energy consumption. For example, by increasing the reflective property of a lighting fixture, only 90% of power may be required to provide the same light output as a similar lighting fixture that is not provided with improved reflective properties. Accordingly, a ballast configured with a ballast factor of 0.90 can be substituted for a ballast configured with ballast factor of 1.0, which provides a corresponding reduction of power that is required for the associated light output. Unfortunately, replacing one ballast having a first ballast factor rating with another ballast having a different ballast factor rating can be very expensive.
In order to accommodate substituting a first ballast with a first ballast factor with a second ballast having a second, different ballast factor in the prior art, two physically separate ballasts must be provided and installed. Although different ballasts may have respective ratings, each ballast is accordingly rated with a respective ballast factor. Thus, lighting designers are constrained to designing building lighting by predetermined ballasts and/or fixtures that combine lamps with ballasts.
Typically, building lighting designers are constrained by various specifications, including reconciling a desired amount of light output with physical limitations in connection with individual ballasts, each configured with a single, permanent ballast factor. This and other constraints experienced by building lighting designers often negatively impact the lighting design process, and, ultimately, the lighting system of a building, because various features desired by a lighting designer may be cost-prohibitive, impractical or both. This may be, for example in case a ballast having a particular ballast factor that is desired by a building lighting designer must be procured by a special order.
Ballast manufacturers typically only make available ballasts in a limited number of ballast factors. Thus, customers can only obtain a limited number of ballast factors for a ballast/lamp configuration.
In addition to various constraints imposed on lighting designers, such as described above, prior art ballasts having a fixed and permanent ballast factor may be difficult or even impossible to replace. Occasionally, specially ordered ballasts, each having a custom ballast factor, such as 0.73, are purchased to accommodate a unique lighting design and build project. Eventually, one or more of the ballasts may fail and need to be replaced. Replacing the custom ballast may be difficult, or very expensive, in the case where the original manufacturer is no longer in business, is not available, or otherwise not manufacturing a ballast having the same custom ballast factor.
FIG. 1 is a diagram illustrating an example of the parties associated with designing, manufacturing and distributing lighting control systems, specifically, fluorescent lighting control systems including ballasts, in connection with the design and construction of a building 10. A building lighting designer 12 designs lighting for one or more areas in the building 10, which is owned by a customer 14. The lighting designer 12 is typically provided with preferred building specifications and provides lighting designs that attempt to comply with the specifications. Typically, the lighting designers 12 are constrained by physical and technical limitations of ballasts, particularly with respect to ballast factors and rated light output associated with a particular lamp and ballast combination. The lighting designer 12 determines a ballast (which is characterized by a desired ballast factor) and a lighting fixture (including a fluorescent lamp type) to use.
The customer 14 may then purchase the ballast directly from a ballast manufacturer 16, or as part of the lighting fixture from an original equipment manufacturer (“OEM”) 18. If the customer 14 places an order for the ballast from a customer service department 20 of the ballast manufacturer 16, the ballast manufacturer ships the ballast directly to the building 10. The ballast manufacturer 16 may have a warehouse 22 or other facility for manufacturing ballasts, and/or for storing the ballasts. If the customer 14 buys the ballast directly from the ballast manufacturer 16, the customer 14 also places an order for the desired lighting fixture with a customer service department 24 of the OEM 18 and the OEM ships the lighting fixture from a warehouse 26 to the building 10. Accordingly, a third party, such as an electrical contractor 28, installs the ballast and the lighting fixture together in the building.
Alternatively, the OEM 18 may provide the ballasts installed in the lighting fixtures that the OEM ships. The OEM 18 preferably orders the ballasts from the ballast manufacturer 16 and stores the ballasts in the warehouse 26. The customer 14 may place an order for the ballast and the lighting fixture from the OEM 18, which then installs the ballast in the lighting fixture and ships the lighting fixture from the warehouse 26 to the building 10. The electrical contactor 28 installs the lighting fixture with the ballast in the building 10.
The ballast manufacturer 16 may employ or otherwise control field service personnel 30 who configure and service the ballasts and the lighting control system in the building 10. The field service personnel 30 travel to the building 10 and service the ballasts, i.e., configure and maintain the ballasts and associated fluorescent lighting control systems. The customer 14 may be trained, for example, by the field service personnel 30, in one or more applications associated with the fluorescent lighting control system. Alternatively, the customer 14 may be authorized to configure the ballasts, such as to define the high-end trim, the low-end trim, occupancy levels, grouping of devices or the like, rather than the field service personnel 30.
Electrical code review personnel 32 review technical specifications and lighting designs, for example, to assess whether a building design complies with building regulations and codes, such as energy efficiency regulations, wiring codes, etc., as defined by state and local governments. The electrical code review personnel 32 may also determine whether a particular building lighting design operates in compliance with power companies' credits and benefits in connection with load shedding.
Since the customer 14 can only order ballasts having a limited number of ballast factors from the ballast manufacturer 16 or the OEM 18, the lighting designer 12 must design the lighting system of the building 10, specifically, the types and locations of the lamps, fixtures, and ballasts, based on these limited numbers of ballast factors. Thus, compromises in the light output or the energy consumption of the lighting system must be made when selecting one of the limited number of ballast factors.
Therefore, there is a need for a method of offering ballasts having any ballast factor desired by the lighting designer 12 and the customer 14.